<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            box-sizing: border-box;
            margin: 0;
        }
        .div1{
            width: 500px;
            height: 250px;
            border-radius: 30px;
            border-width: 8px;
            border-color:rgb(0, 123, 255);
            border-style: solid;
            padding: 10px;
            text-align: center;
            /* margin-left:30px;
            margin-top: 100px; */
            /* margin: 0 auto; */
            margin-top:50% auto;
            margin-left: auto;
            margin-right: auto;
            margin-bottom: auto;
        }
        /* .div2{
            width: 250px;
            height: 120px;
            border-radius: 30px;
            border-width: 8px;
            border-color:rgb(0, 255, 179);
            border-style: solid;
            padding: 8px;
        } */
    </style>
</head>
<body>
    <div class="div1">
        hello world
        <!-- <div >
            nihao
        </div> -->
    </div>
</body>
</html>